The present invention relates to a device and to a method for generating a signal having an adjustable pulse duty factor, and to a pulse-width-modulation device and a voltage converter.
Pulse-width modulation (PWM) is a highly widespread technique. It is used in many areas of application, for example in the area of controlling power electronics or for current or voltage conversion. There are numerous other areas of application as well.
A PWM signal is normally a square wave signal having a constant period. During this period, the signal can assume a first state within a first time interval and can assume a second state in the time remaining in the period. The ratio of the time intervals in which the signal assumes the first and the second state is referred to as the pulse duty factor.
In order to digitally generate PWM signals, a counter can be used, for example, which periodically counts from zero up to a predetermined maximum value at a predefined clock frequency. Once the maximum value has been reached, the counter is reset and restarts at zero. Therefore, the clock frequency, in combination with the maximum value of the counter, determines the period of the PWM signal to be generated. The resolution of the pulse duty factor, which can be adjusted in this way, is determined via the clock frequency of the counter.
European patent application EP 1 653 618 A2 discloses a PWM generator having an increased resolution of the pulse duty factor. An additional generator is proposed for this purpose, which is clocked with a period which corresponds to a small fraction of the maximum PWM period.
Therefore, there is a need for a simple and efficient generation of signals having a precisely adjustable pulse duty factor.